x86 SMM: Replace weak prototypes with weak function stub

Change-Id: I682617cd2f4310d3e2e2ab6ffec51def28a4779c
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/7961
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/src/southbridge/intel/i82801dx/smihandler.c b/src/southbridge/intel/i82801dx/smihandler.c
index e5a3282..6375876 100644
--- a/src/southbridge/intel/i82801dx/smihandler.c
+++ b/src/southbridge/intel/i82801dx/smihandler.c
@@ -441,12 +441,10 @@
 
 	reg16 &= inw(pmbase + ALT_GP_SMI_EN);
 
-	if (mainboard_smi_gpi) {
-		mainboard_smi_gpi(reg16);
-	} else {
-		if (reg16)
-			printk(BIOS_DEBUG, "GPI (mask %04x)\n",reg16);
-	}
+	mainboard_smi_gpi(reg16);
+
+	if (reg16)
+		printk(BIOS_DEBUG, "GPI (mask %04x)\n",reg16);
 }
 
 static void southbridge_smi_mc(unsigned int node, smm_state_save_area_t *state_save)